The present invention relates to an electrophotographic recording material comprised of an electrically conductive support, an optional insulating interlayer, and a photoconductive single layer containing a pyrimido[5',4':5,6]pyrido-[1,2a]benzimidazole derivative as the photoconductor, a binder, and a dye or pigment in homogeneous solution or disperse distribution as a sensitizer. The present invention relates in particular to an electrophotographic recording material for a lithographic printing form or a printed circuit, that can be prepared by an electrophotographic method when binders which can be stripped under alkaline conditions are present in the photoconductive layer.
Certain pyrimido[5',4':5,6]pyrido-[1,2a]benzimidazole compounds are known. These have been generally described in German Offenlegungsschrift No. 2,929,414 as fluorescent brighteners, as fluorescence dyes, and even as photoconductors. Their unusually good photoconductive properties in binders which can be stripped, especially under alkaline conditions, were neither described nor suggested, however. Instead, the range of application of the compounds was very restricted, due to their low solubility properties and poor film-forming properties.
The maximum absorption of most of the compounds known as organic photoconductors, such as oxazole, oxadiazole, pyrazoline and phenylhydrazone derivatives and also polyvinylcarbazole, is below the 400 nm wavelength. In the presence of binders, the photoconductive layers are in most cases transparent to light in the spectral region above 430 nm, so that, without sensitization, they are photosensitive only in the near-ultraviolet region.